Imaging module and reader for, and method of, expeditiously setting imaging parameters of imagers for imaging targets to be read over a range of working distances

ABSTRACT

An imaging reader has near and far imagers for imaging illuminated targets to be read over a range of working distances. A range finder determines a distance to a target. A default imager captures a minor portion of an image of the target, and rapidly determines its light intensity level. At least one of the imagers is selected based on the determined distance and/or the determined light intensity level. The exposure and/or gain of the selected imager is set to a predetermined value, and an illumination level is determined, also based on the determined light intensity level and/or the determined distance. The selected imager, which has been set with the predetermined value, captures an image of the target, which has been illuminated at the illumination light level.

BACKGROUND OF THE INVENTION

The present invention relates generally to an imaging module and animaging reader for, and a method of, expeditiously setting one or moreimaging parameters, such as exposure and/or gain values, of at least oneimager for imaging targets to be electro-optically read by image captureover a range of working distances.

Solid-state imaging systems or imaging readers have been used, in bothhandheld and/or hands-free modes of operation, to electro-optically readtargets, such as one- and two-dimensional bar code symbol targets,and/or non-symbol targets, such as documents. A handheld imaging readerincludes a housing having a handle held by an operator, and an imagingmodule, also known as a scan engine, supported by the housing and aimedby the operator at a target during reading. The imaging module includesan imaging assembly having a solid-state imager or imaging sensor withan imaging array of photocells or light sensors, which correspond toimage elements or pixels in an imaging field of view of the imager, andan imaging lens assembly for capturing return light scattered and/orreflected from the target being imaged, and for projecting the returnlight onto the array to initiate capture of an image of the target. Suchan imager may include a one- or two-dimensional charge coupled device(CCD) or a complementary metal oxide semiconductor (CMOS) device andassociated circuits for producing and processing electronic signalscorresponding to a one- or two-dimensional array of pixel data over theimaging field of view. In order to increase the amount of the returnlight captured by the array, for example, in dimly lit environments, theimaging module generally also includes an illuminating light assemblyfor illuminating the target with illumination light in an illuminationpattern for reflection and scattering from the target.

In some applications, for example, in warehouses, it is sometimesnecessary for the same reader to read not only far-out targets, e.g., onproducts located on high overhead shelves, which are located at afar-out range of working distances on the order of thirty to fifty feetaway from the reader, but also close-in targets, e.g., on productslocated at floor level or close to the operator, which are located at aclose-in range of working distances on the order of less than two feetaway from the reader. The reader may illuminate the far-out targets byemitting an illumination light at an intense, bright level, andcapturing the return light from the illuminated far-out targets byemploying a far-out imager having a relatively narrow field of view, andmay illuminate the close-in targets by emitting the illumination lightat a less intense, dimmer level, and capturing the return light from theilluminated close-in targets by employing a close-in imager having arelatively wide field of view. This variable illumination light levelenables each such target to be more reliably imaged and successfullyread.

However, the use of more than one imager and the variable illuminationlevel presents a challenge to reader performance. For optimum readerperformance, each target must be read by the correct imager; the correctimager should be set with one or more optimum imaging parameters, suchas exposure values and/or gain values; and the illumination light shouldbe set at an optimum illumination light level or value. These values aredifferent for each imager, and vary, among other things, as a functionof the working distance and of the illumination light level. Increasingthe exposure and/or the gain values of the imager, as well as increasingthe illumination light level, will increase the captured imagebrightness of the image of the target, and vice versa.

In order to set an imager with one or more optimum imaging parameters,it is known for the imager to capture an entire image from the target,to analyze the brightness of the entire image, to change the imagingparameters based on the analysis of the entire image, to capture anotherentire image from the target, and to repeat all the steps of thisprocess for as many times as it takes until the brightness of the entireimage is within an acceptable level. An automatic exposure controller(AEC) is typically used to control the imager's exposure, and anautomatic gain controller (AGC) is typically used to control theimager's gain. A typical known strategy is to use exposure priority, inwhich the exposure is increased first until a maximum exposure time orthreshold (typically around 4-8 ms in order to reduce hand jitter motioneffects for a handheld reader) is reached. If the image brightness isstill too low, then the gain is increased. This strategy maximizes thesignal-to-noise ratio (SNR) of the imager, because the gain is onlyincreased when necessary. Although generally satisfactory for itsintended purpose, this known process is very slow and inefficient inpractice, especially when more than one imager is involved, and when theentire known process has to be repeated for each additional imager.Reader performance can be deemed sluggish, and is unacceptable in manyapplications.

Accordingly, there is a need to expeditiously select the correct imagerin such readers, to expeditiously set the selected imager with one ormore optimum imaging parameters, and to expeditiously set theilluminating light assembly to illuminate the target with illuminationlight at an optimum illumination light level, in order to more rapidly,efficiently, reliably, and successfully read both far-out targets andclose-in targets with the same reader.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying figures, where like reference numerals refer toidentical or functionally similar elements throughout the separateviews, together with the detailed description below, are incorporated inand form part of the specification, and serve to further illustrateembodiments of concepts that include the claimed invention, and explainvarious principles and advantages of those embodiments.

FIG. 1 is a side elevational view of a portable imaging reader operativefor reading targets by image capture over an extended range of workingdistances in accordance with this disclosure.

FIG. 2 is a schematic diagram of various components, including imaging,illuminating, and range finding assemblies supported on an imagingmodule that is mounted inside the reader of FIG. 1.

FIG. 3 is a perspective view of the imaging module of FIG. 2 inisolation.

FIG. 4 is a cross-sectional view taken on line 4-4 of FIG. 3.

FIG. 5 is a cross-sectional view taken on line 5-5 of FIG. 3.

FIG. 6 is a vertical sectional view taken on line 6-6 of FIG. 3.

FIG. 7 is a flow chart depicting steps performed in accordance with amethod of this disclosure.

Skilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions and locations of some of theelements in the figures may be exaggerated relative to other elements tohelp to improve understanding of embodiments of the present invention.

The system and method components have been represented where appropriateby conventional symbols in the drawings, showing only those specificdetails that are pertinent to understanding the embodiments of thepresent invention so as not to obscure the disclosure with details thatwill be readily apparent to those of ordinary skill in the art havingthe benefit of the description herein.

DETAILED DESCRIPTION OF THE INVENTION

One aspect of the present disclosure relates to an imaging module, alsoknown as a scan engine, for setting one or more imaging parameters,e.g., exposure and/or gain values, of at least one imager for imagingtargets to be electro-optically read over a range of working distancesaway from the module. Another aspect of the present disclosure relatesto an imaging reader having a housing for supporting the imaging module,and a light-transmissive window on the housing.

In both aspects, the imaging module comprises an imaging assemblyincluding a near imager for imaging targets over a relatively widerimaging field of view, and a far imager for imaging targets over arelatively narrower imaging field of view. An illuminating lightassembly illuminates targets with illumination light. A range finderdetermines a distance to a target. A main controller or programmedmicroprocessor controls a default one of the imagers, for example, thefar imager, to capture a minor portion of an image of the target,determines a light intensity level of the captured minor portion of theimage, selects at least one of the imagers based on the determineddistance and/or the determined light intensity level, and controls theilluminating light assembly to illuminate the target with illuminationlight at an illumination light level based on the determined distanceand/or the determined light intensity level. In addition, the maincontroller sets at least one of the imaging parameters of the selectedat least one imager to a predetermined value based on the determinedlight intensity level and/or the determined distance, and controls theselected at least one imager, which has been set with the predeterminedvalue, to capture an image of the target, which has been illuminated atthe illumination light level.

A memory is accessible to the main controller and stores a plurality ofpredetermined values, e.g., exposure values and/or gain values, of theat least one imaging parameter for retrieval by the main controller froma look-up table. These predetermined values are different based on thedetermined light intensity level and/or the determined distance.Advantageously, the default imager is controlled by the main controllerto operate at a predetermined frame rate, e.g., 60 frames per second(fps). The main controller determines the light intensity level from theminor portion of the image at a rate faster than the predetermined framerate. By way of numerical example, if the image is subdivided into fourquadrants, then the minor portion of the image can be one of thesequadrants, in which case, the main controller can determine the lightintensity level from the minor portion of the image at a rate that isfour times faster, e.g., 240 fps, than the predetermined frame rate.Thus, the selected imager is more rapidly and efficiently set withoptimum exposure values and/or gain values than heretofore.

Still another aspect of the present disclosure relates to a method ofsetting one or more imaging parameters of at least one imager forimaging targets to be electro-optically read over a range of workingdistances. The method is performed by providing a near imager to imagetargets over a relatively wider imaging field of view, by providing afar imager to image targets over a relatively narrower imaging field ofview, by providing an illuminator to illuminate targets withillumination light, and by determining a distance to a target. Themethod is further performed by controlling a default one of the imagers,e.g., the far imager, to capture a minor portion of an image of thetarget, by determining a light intensity level of the captured minorportion of the image, by selecting at least one of the imagers based onthe determined distance and/or the determined light intensity level, bycontrolling the illuminating light assembly to illuminate the targetwith illumination light at an illumination light level based on thedetermined distance and/or the determined light intensity level, and bysetting the at least one imaging parameter of the selected at least oneimager to a predetermined value based on the determined light intensitylevel and/or the determined distance. The method is still furtherperformed by controlling the selected at least one imager, which hasbeen set with the predetermined value, to capture an image of thetarget, which has been illuminated at the illumination light level.

Reference numeral 30 in FIG. 1 generally identifies an ergonomic imagingreader configured as a gun-shaped housing having an upper barrel or body32 and a lower handle 28 tilted rearwardly away from the body 32 at anangle of inclination, for example, fifteen degrees, relative to thevertical. A light-transmissive window 26 is located adjacent the frontor nose of the body 32 and is preferably also tilted at an angle ofinclination, for example, fifteen degrees, relative to the vertical. Theimaging reader 30 is held in an operator's hand and used in a handheldmode in which a trigger 34 is manually depressed to initiate imaging oftargets, especially bar code symbols, to be read in an extended range ofworking distances, for example, on the order of thirty to fifty feet,away from the window 26. Housings of other configurations, as well asreaders operated in the hands-free mode, could also be employed.

As schematically shown in FIG. 2, and as more realistically shown inFIGS. 3-6, an imaging module 10 is mounted in the reader 30 behind thewindow 26 and is operative, as described below, for expeditiouslysetting one or more imaging parameters, e.g., exposure and/or gainvalues, of an imager for imaging targets to be electro-optically read byimage capture through the window 26 over an extended range of workingdistances away from the module 10. A target may be located anywhere in aworking range of distances between a close-in working distance (WD1) anda far-out working distance (WD2). In a preferred embodiment, WD1 iseither at, or about eighteen inches away, from the window 26, and WD2 ismuch further away, for example, over about sixty inches away from thewindow 26. An intermediate working distance between WD1 and WD2 is abouteighteen to about sixty inches away from the window 26. The module 10includes an imaging assembly that has a near imaging sensor or imager12, and a near imaging lens assembly 16 for capturing return light overa relatively wide imaging field of view 20, e.g., about thirty degrees,from a near target located in a close-in region of the range, e.g., fromabout zero inches to about eighteen inches away from the window 26, andfor projecting the captured return light onto the near imager 12, aswell as a far imaging sensor or imager 14, and a far imaging lensassembly 18 for capturing return light over a relatively narrow imagingfield of view 22, e.g., about sixteen degrees, from a far target locatedin a far-out region of the range, e.g., greater than about sixty inchesaway from the window 26, and for projecting the captured return lightonto the far imager 14. Although only two imagers 12, 14 and two imaginglens assemblies 16, 18 have been illustrated in FIG. 2, it will beunderstood that more than two could be provided in the module 10.

Each imager 12, 14 is a solid-state device, for example, a CCD or a CMOSimager having a one-dimensional array of addressable image sensors orpixels arranged in a single, linear row, or preferably a two-dimensionalarray of such sensors arranged in mutually orthogonal rows and columns,and operative for detecting return light captured by the respectiveimaging lens assemblies 16, 18 along respective imaging axes 24, 36through the window 26. Each imaging lens assembly is advantageously aCooke triplet, although other fixed focus and variable focus lenscombinations can also be employed.

As also shown in FIGS. 2 and 4, an illuminating light assembly is alsosupported by the imaging module 10 and includes an illumination lightsource, e.g., at least one light emitting diode (LED) 40, stationarilymounted on an optical axis 42, and an illuminating lens assembly thatincludes an illuminating lens 44 also centered on the optical axis 42.The illuminating light assembly is shared by both imagers 12, 14. Asfurther shown in FIGS. 2, 5 and 6, an aiming light assembly is alsosupported by the imaging module 10 and includes an aiming light source46, e.g., a laser, stationarily mounted on an optical axis 48, and anaiming lens 50 centered on the optical axis 48. The aiming lens 50 maybe a diffractive or a refractive optical element, and is operative forprojecting a visible aiming light pattern on the target prior toreading.

As further shown in FIG. 2, the imagers 12, 14, the LED 40 and the laser46 are operatively connected to a main controller or programmedmicroprocessor 52 operative for controlling the operation of thesecomponents. A memory 54 is connected and accessible to the controller52. Preferably, the controller 52 is the same as the one used forprocessing the return light from the targets and for decoding thecaptured target images.

The aforementioned aiming light assembly also serves as a range finderto determine the distance to a target. The aiming axis 48 is offset fromthe imaging axes 24, 36 so that the resulting parallax provides targetdistance information. More particularly, the parallax between the aimingaxis 48 and either one of the imaging axes 24, 36 provides rangeinformation from the pixel position of the aiming beam on one of theimaging sensor arrays. It is preferred to use the imaging axis 36 of thefar imager 14, because the parallax error will be greater for the farimager 14 than for the near imager 12. It will be understood that othertypes of range finders, e.g., acoustic devices, can be employed todetermine the target distance. Thus, the range finder locates the targetto determine whether the target is in a close-in region, or anintermediate region, or a far-out region, of the range.

In operation, the main controller 52 controls a default one of theimagers, for example, the far imager 14, to capture a minor orfractional portion of an image of the target. For example, if the imageis comprised of a two-dimensional array of pixels arranged in apredetermined row number (M) of rows and a predetermined column number(N) of columns, then the minor portion of the image is comprised of asubarray of pixels arranged in a number of rows less than M and in anumber of columns less than N. The subarray can be located anywhere onthe image; for example, it can be in a corner or central area of theimage, or it can be the area of the image covered by the aiming lightpattern.

The main controller 52 then determines a light intensity level of thecaptured minor portion of the image. This is performed much faster thanin the known art where the light intensity level had to be determinedfrom the entire image. For example, if the default far imager 14operates at a predetermined frame rate, e.g., 60 frames per second(fps), and if the image is subdivided into four quadrants, then the maincontroller 52 can determine the light intensity level from the minorportion or quadrant at a rate that is four times faster, e.g., 240 fps,than the predetermined frame rate.

The main controller 52 then selects either the near imager 12 or the farimager 14 based on the determined distance and/or the determined lightintensity level. Once the correct imager has been selected, the maincontroller 52 then sets the one or more imaging parameters, e.g.,exposure and/or gain values, of the selected imager to a predeterminedor optimum value based on the determined light intensity level and/orthe determined distance. The aforementioned memory 54 stores a set ofexposure values and/or a set of gain values in a look-up table 60. Themain controller 52 has a gain controller 56 that can access the look-uptable 60 and retrieve the correct gain value that corresponds to thedetermined distance and/or the determined light intensity level. Themain controller 52 also has an exposure controller 58 that can accessthe look-up table 60 and retrieve the correct exposure value thatcorresponds to the determined distance and/or the determined lightintensity level. Each set of exposure and gain values includes a rangeof different values, and is determined in advance by knowledge of theF-stop and responsivity of each imager as a function of distance awayfrom the respective imager and/or the light intensity level.

The main controller 52 also controls the illuminating light assembly toilluminate the target with illumination light at an illumination lightlevel based on the determined distance and/or the determined lightintensity level. The main controller 52 energizes the illuminating lightassembly to illuminate the target with illumination light of arelatively lesser intensity when the range finder determines that thetarget to be imaged and read is located in a close-in region of therange; or energizes the illuminating light assembly to illuminate thetarget with illumination light of a relatively greater intensity whenthe range finder determines that the target to be imaged and read islocated in a far-out region of the range; or energizes the illuminatinglight assembly to illuminate the target with illumination light of arelatively intermediate intensity that is between the lesser intensityand the greater intensity when the range finder determines that thetarget to be imaged and read is located in an intermediate region thatis between the close-in region and the far-out region of the range.

More particularly, the main controller 52 energizes the LED 40 with avariable electrical current to vary the intensity or level of theillumination light. By way of non-limiting numerical example, theelectrical current is on the order of 30 milliamperes when the close-inregion lies between about 0.0 inches and about eighteen inches from thewindow 26, is on the order of 150 milliamperes when the intermediateregion lies between about eighteen inches and about sixty inches fromthe window 26, and is on the order of 600 milliamperes when the far-outregion lies between about sixty inches and infinity from the window 26.The main controller 52 varies the intensity of the illumination lighteither as a continuous analog function, or as a stepwise, multi-levelfunction, of the distance determined by the range finder.

Once the correct imager has been selected by the main controller 52, andonce the gain and/or exposure values for the selected imager have beenset by the gain and exposure controllers 56, 58, and once theillumination light level has been determined by the main controller 52,then the selected imager is operated by the main controller 52 tocapture an image of the target to be read. Reader performance is rapidand aggressive.

The flow chart of FIG. 7 depicts the method disclosed herein. In step100, the minor portion of the image of the target is captured by one ofthe imagers by default, e.g., the far imager 14. In step 102, the lightintensity level of the captured minor portion of the image isdetermined, and the distance to the target is also determined. Eitherthe far imager 14 or the near imager 12 may be selected based on thedetermined distance and/or the determined light intensity level in step104. The target is illuminated with illumination light whoseillumination level is also based on the determined distance and/or thedetermined light intensity level in step 106. Then, optimum exposureand/or gain values are set for the selected imager in step 108 byreferral to the look-up table 60. In step 110, the selected imager,whose exposure and/or gain has already been set, captures an image ofthe target, which has been illuminated at the illumination light level.

In the foregoing specification, specific embodiments have beendescribed. However, one of ordinary skill in the art appreciates thatvarious modifications and changes can be made without departing from thescope of the invention as set forth in the claims below. Accordingly,the specification and figures are to be regarded in an illustrativerather than a restrictive sense, and all such modifications are intendedto be included within the scope of present teachings.

The benefits, advantages, solutions to problems, and any element(s) thatmay cause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeatures or elements of any or all the claims. The invention is definedsolely by the appended claims including any amendments made during thependency of this application and all equivalents of those claims asissued.

Moreover in this document, relational terms such as first and second,top and bottom, and the like may be used solely to distinguish oneentity or action from another entity or action without necessarilyrequiring or implying any actual such relationship or order between suchentities or actions. The terms “comprises,” “comprising,” “has,”“having,” “includes,” “including,” “contains,” “containing,” or anyother variation thereof, are intended to cover a non-exclusiveinclusion, such that a process, method, article, or apparatus thatcomprises, has, includes, contains a list of elements does not includeonly those elements, but may include other elements not expressly listedor inherent to such process, method, article, or apparatus. An elementproceeded by “comprises . . . a,” “has . . . a,” “includes . . . a,” or“contains . . . a,” does not, without more constraints, preclude theexistence of additional identical elements in the process, method,article, or apparatus that comprises, has, includes, or contains theelement. The terms “a” and “an” are defined as one or more unlessexplicitly stated otherwise herein. The terms “substantially,”“essentially,” “approximately,” “about,” or any other version thereof,are defined as being close to as understood by one of ordinary skill inthe art, and in one non-limiting embodiment the term is defined to bewithin 10%, in another embodiment within 5%, in another embodimentwithin 1%, and in another embodiment within 0.5%. The term “coupled” asused herein is defined as connected, although not necessarily directlyand not necessarily mechanically. A device or structure that is“configured” in a certain way is configured in at least that way, butmay also be configured in ways that are not listed.

It will be appreciated that some embodiments may be comprised of one ormore generic or specialized processors (or “processing devices”) such asmicroprocessors, digital signal processors, customized processors, andfield programmable gate arrays (FPGAs), and unique stored programinstructions (including both software and firmware) that control the oneor more processors to implement, in conjunction with certainnon-processor circuits, some, most, or all of the functions of themethod and/or apparatus described herein. Alternatively, some or allfunctions could be implemented by a state machine that has no storedprogram instructions, or in one or more application specific integratedcircuits (ASICs), in which each function or some combinations of certainof the functions are implemented as custom logic. Of course, acombination of the two approaches could be used.

Moreover, an embodiment can be implemented as a computer-readablestorage medium having computer readable code stored thereon forprogramming a computer (e.g., comprising a processor) to perform amethod as described and claimed herein. Examples of suchcomputer-readable storage mediums include, but are not limited to, ahard disk, a CD-ROM, an optical storage device, a magnetic storagedevice, a ROM (Read Only Memory), a PROM (Programmable Read OnlyMemory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM(Electrically Erasable Programmable Read Only Memory) and a Flashmemory. Further, it is expected that one of ordinary skill,notwithstanding possibly significant effort and many design choicesmotivated by, for example, available time, current technology, andeconomic considerations, when guided by the concepts and principlesdisclosed herein, will be readily capable of generating such softwareinstructions and programs and ICs with minimal experimentation.

The Abstract of the Disclosure is provided to allow the reader toquickly ascertain the nature of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims. In addition, in theforegoing Detailed Description, it can be seen that various features aregrouped together in various embodiments for the purpose of streamliningthe disclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments require morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive subject matter lies in less than allfeatures of a single disclosed embodiment. Thus, the following claimsare hereby incorporated into the Detailed Description, with each claimstanding on its own as a separately claimed subject matter.

The invention claimed is:
 1. An imaging module for setting at least oneimaging parameter of at least one imager for imaging targets to beelectro-optically read over a range of working distances away from themodule, the module comprising: an imaging assembly including a nearimager for imaging targets over a relatively wider imaging field ofview, and a far imager for imaging targets over a relatively narrowerimaging field of view, the near imager being separate from the farimager; an illuminating light assembly for illuminating targets withillumination light; a range finder for determining a distance to atarget; and a main controller for controlling only a default one of theimagers to capture a minor portion of an image of the target, fordetermining a light intensity level of the captured minor portion of theimage, for selecting at least one of the imagers based on at least oneof the determined distance and the determined light intensity level, forcontrolling the illuminating light assembly to illuminate the targetwith illumination light at an illumination light level based on the atleast one of the determined distance and the determined light intensitylevel, for setting the at least one imaging parameter of the selected atleast one imager to a predetermined value based on the at least one ofthe determined light intensity level and the determined distance, andfor controlling the selected at least one imager, which has been setwith the predetermined value, to capture an image of the target, whichhas been illuminated at the illumination light level.
 2. The module ofclaim 1, and a memory accessible to the main controller for storing aplurality of predetermined values of the at least one imaging parameterfor retrieval by the main controller, and wherein the predeterminedvalues are different based on the at least one of the determined lightintensity level and the determined distance.
 3. The module of claim 2,wherein the main controller includes an exposure controller and a gaincontroller, wherein the plurality of predetermined values stored in thememory include a set of exposure values for retrieval by the exposurecontroller and a set of gain values for retrieval by the gaincontroller, wherein the exposure values are different based on the atleast one of the determined light intensity level and the determineddistance, and wherein the gain values are different based on the atleast one of the determined light intensity level and the determineddistance.
 4. The module of claim 1, wherein the default imager iscontrolled by the main controller to operate at a predetermined framerate, and wherein the main controller determines the light intensitylevel from the minor portion of the image at a rate faster than thepredetermined frame rate.
 5. The module of claim 1, wherein the image iscomprised of pixels arranged in a predetermined row number of rows and apredetermined column number of columns, and wherein the minor portion ofthe image is comprised of pixels arranged in a number of rows less thanthe predetermined row number and in a number of columns less than thepredetermined column number.
 6. The module of claim 1, wherein the maincontroller is operative for controlling the illuminating light assemblyto illuminate the target with illumination light having a relativelylesser illumination light level when the range finder determines thatthe target to be imaged and read is located in a close-in region of therange, for controlling the illuminating light assembly to illuminate thetarget with illumination light of a relatively greater illuminationlight level when the range finder determines that the target to beimaged and read is located in a far-out region of the range, and forcontrolling the illuminating light assembly to illuminate the targetwith illumination light of a relatively intermediate illumination lightlevel that is between the lesser illumination light level and thegreater illumination light level when the range finder determines thatthe target to be imaged and read is located in an intermediate regionthat is between the close-in region and the far-out region of the range.7. The module of claim 1, wherein the main controller varies theillumination light level as one of a continuous and a stepwise functionbased on the at least one of the determined distance and the determinedlight intensity level.
 8. The module of claim 1, wherein each imagercaptures return light from the target along an optical axis, and whereinthe range finder includes an aiming assembly for emitting an aiming beamalong an aiming axis that is offset from at least one of the opticalaxes.
 9. An imaging reader for reading targets by image capture over arange of working distances away from the reader, comprising: a housinghaving a light-transmissive window; and an imaging module for setting atleast one imaging parameter of at least one imager for imaging thetargets, the module including an imaging assembly including a nearimager for imaging targets over a relatively wider imaging field ofview, and a far imager for imaging targets over a relatively narrowerimaging field of view, the near imager being separate from the farimager, an illuminating light assembly for illuminating targets withillumination light, a range finder for determining a distance to atarget, and a main controller for controlling only a default one of theimagers to capture a minor portion of an image of the target, fordetermining a light intensity level of the captured minor portion of theimage, for selecting at least one of the imagers based on at least oneof the determined distance and the determined light intensity level, forcontrolling the illuminating light assembly to illuminate the targetwith illumination light at an illumination light level based on the atleast one of the determined distance and the determined light intensitylevel, for setting the at least one imaging parameter of the selected atleast one imager to a predetermined value based on the at least one ofthe determined light intensity level and the determined distance, andfor controlling the selected at least one imager, which has been setwith the predetermined value, to capture an image of the target, whichhas been illuminated at the illumination light level.
 10. The reader ofclaim 9, and a memory accessible to the main controller for storing aplurality of predetermined values of the at least one imaging parameterfor retrieval by the main controller, and wherein the predeterminedvalues are different based on the at least one of the determined lightintensity level and the determined distance.
 11. The reader of claim 10,wherein the main controller includes an exposure controller and a gaincontroller, wherein the plurality of predetermined values stored in thememory include a set of exposure values for retrieval by the exposurecontroller and a set of gain values for retrieval by the gaincontroller, wherein the exposure values are different based on the atleast one of the determined light intensity level and the determineddistance, and wherein the gain values are different based on the atleast one of the determined light intensity level and the determineddistance.
 12. The reader of claim 9, wherein the default imager iscontrolled by the main controller to operate at a predetermined framerate, and wherein the main controller determines the light intensitylevel from the minor portion of the image at a rate faster than thepredetermined frame rate.
 13. The reader of claim 9, wherein the imageis comprised of pixels arranged in a predetermined row number of rowsand a predetermined column number of columns, and wherein the minorportion of the image is comprised of pixels arranged in a number of rowsless than the predetermined row number and in a number of columns lessthan the predetermined column number.
 14. A method of setting at leastone imaging parameter of at least one imager for imaging targets to beelectro-optically read over a range of working distances, the methodcomprising: providing a near imager to image targets over a relativelywider imaging field of view; providing a far imager to image targetsover a relatively narrower imaging field of view, the near imager beingseparate from the far imager; providing an illuminator to illuminatetargets with illumination light; determining a distance to a target;controlling only a default one of the imagers to capture a minor portionof an image of the target; determining a light intensity level of thecaptured minor portion of the image; selecting at least one of theimagers based on at least one of the determined distance and thedetermined light intensity level; controlling the illuminating lightassembly to illuminate the target with illumination light at anillumination light level based on the at least one of the determineddistance and the determined light intensity level; setting the at leastone imaging parameter of the selected at least one imager to apredetermined value based on the at least one of the determined lightintensity level and the determined distance; and controlling theselected at least one imager, which has been set with the predeterminedvalue, to capture an image of the target, which has been illuminated atthe illumination light level.
 15. The method of claim 14, and storing aplurality of predetermined values of the at least one imaging parameter,and configuring the predetermined values to be different based on the atleast one of the determined light intensity level and the determineddistance.
 16. The method of claim 15, and storing the plurality ofpredetermined values as a set of exposure values and as a set of gainvalues, and configuring the exposure values to be different based on theat least one of the determined light intensity level and the determineddistance, and configuring the gain values to be different based on theat least one of the determined light intensity level and the determineddistance.
 17. The method of claim 14, and controlling the default imagerto operate at a predetermined frame rate, and wherein the lightintensity level is determined from the minor portion of the image at arate faster than the predetermined frame rate.
 18. The method of claim14, and configuring the image of pixels arranged in a predetermined rownumber of rows and a predetermined column number of columns, andconfiguring the minor portion of the image of pixels arranged in anumber of rows less than the predetermined row number and in a number ofcolumns less than the predetermined column number.
 19. The method ofclaim 14, and illuminating the target with illumination light having arelatively lesser illumination light level upon the determination thatthe target to be imaged and read is located in a close-in region of therange, and with illumination light of a relatively greater illuminationlight level upon the determination that the target to be imaged and readis located in a far-out region of the range, and with illumination lightof a relatively intermediate illumination light level that is betweenthe lesser illumination light level and the greater illumination lightlevel upon the determination that the target to be imaged and read islocated in an intermediate region that is between the close-in regionand the far-out region of the range.
 20. The method of claim 14, whereinthe determining of the distance to the target is performed by emittingan aiming beam along an aiming axis that is offset from an optical axisalong which the selected at least one imager captures the image.